The use of oligo-2,6-pyridines as complexing agents that can be incorporated in targeting immunoreagents is disclosed, for example, in WO 92/08494 (PCT/US91/08253).
As discussed in WO 92/08494, these complexing agents solve several problems in the prior art, particularly as regards therapeutic and diagnostic imaging uses of targeting radioactive immunoreagents.
One drawback regarding the oligo-2,6-pyridines is the difficulty and costliness of heretofore known methods for their synthesis. Thus, the synthetic methods disclosed in WO92/08494 involve several difficult, extremely low temperature n-butyllithium reactions which require extremely low and carefully controlled reaction temperatures (-78.degree. C.). The low temperature reactions of n-butyllithium in chemical manufacturing often require special reactors and present problems associated with solubilities of various reactants. It would therefore be very desirable to have alternative synthetic methods for the oligo-2,6-pyridines that require fewer steps and less drastic reaction conditions.